It may seem to go without saying that CT's attempts to modify automatic thoughts, dysfunctional beliefs, and cognitive distortions are responsible for CT's effects and that therefore, that it is important for us to spend time in therapy working on dysfunctional cognitions. However, there are many other aspects of CT that could be responsible for its effectiveness. For example, CT includes "non-specific" factors such as the therapist's empathy and includes many behavioral interventions along with the cognitive interventions. Thus, studies that show that CT works do not necessarily provide evidence that cognitive change is important.

Studies that show that dysfunctional cognitions decrease when depressed individuals are treated with medication alone have led some to conclude that decreases in dysfunctional cognitions are an effect of decreases in depression, not a cause of decreases in depression. In fact, some (Steve Hayes comes to mind) argue that the types of changes in cognition that CT tries to accomplish are unnecessary or are counterproductive.

At this point, we have many studies that show that CBT is effective with a broad range of problems but many fewer studies that examine whether the cognitive changes that CT seeks to achieve have an important influence on outcome. Fortunately, a number of studies have been designed to examine the role that cognitive change plays in the effectiveness of CT.

In a recent study of the multidisciplinary treatment of chronic pain, Burns and his colleagues (Burns, et al, 2003) used a cross-lagged panel design to examine whether cognitive changes were a cause of improvement or an effect of improvement. They found that early-treatment changes in catastrophising and helplessness predicted late-treatment changes in outcome measures but not vice-versa. They also found that early-treatment depression changes predicted late-treatment activity changes but not vice versa. These results provide support for the hypothesis that changes in cognition are a cause of improvement rather than being a result of improvement.

In another recent study, Beevers et al (2003) examined the relationship between degree of cognitive change during treatment for depression and rate of relapse. In a sample of individuals who had achieved at least a 50% improvement in depressive symptoms, the researchers found that both a poor change in dysfunctional attitudes and a poor change in extreme thinking predicted a faster return of depressive symptoms.

Note: This isn't a systematic review, just a couple of studies I've encountered recently, but at least is gives us some support for the idea that achieving cognitive change is important.